Abstract : Postulating the existence of an additional atmospheric absorber it became possible to verify partly Roenicke's radiation measurements within the upper part of a tropical airmass in which strong radiative heating was observed. Heating rates could be duplicated while calculated corresponding flux densities yield values 20% smaller than the measured net flux densities. All calculations were made on the basis of the emissivity function for water vapor which was tabulated for this purpose. (Author)